The Study Of Application And Mechanism On Bioremediation Of Water Oil Pollution By Oil-degrading Bacteria And Biosurfactant

The application and mechanism of oil-degrading strain, biosurfactant andnaphthalene-degrading strain on bioremediation of water oil pollution were studied in this paper.The study included the isolation, identification and characteristics of strains (oil-degradingstrains, biosurfactant-producing strain and naphthalene-degrading strain), effect of biosurfactanton the degradation of oil, the immobilization of oil-degrading strains, the degradation pathwaysof petroleum hydrocarbon, and the mechanism of biosurfactant-producing.Five oil-degrading strains (P1, P2, P3, P4, P5), one biosurfactant-producing strain (S6) andone naphthalene-degrading strain (N7) were isolated from oil-containing wastewater.The experimental results on the characteristics of five oil-degrading strains indicated thatinoculation amount, salinity, oxygen, temperature, oil mass concentration, microorganism ageand nutritious salt had significant effect on oil degradation. The mixed strains community coulddegrade crude oil more effectivelly than any one alone and the best degrading effects (86.4%)would be obtained through orthogonal experiment: P1 0.1%, P2 0.1%, P3 0.4%, P4 0.1%, P50.9%, respectively. The experiment showed that immobilization bv wood crumbs couldaccelerate the degradation of crude oil. GC-MS analysis revealed that five crude oil-degradingstrains had better effect on degrading C₇～C₁₇ straight chain alkanes. Confocal laser scanningmicroscopy analysis revealed that concentration of n-heptane, n-tetradecane and metabolitesabsorbed in membrane were increased. GC analysis verified that alkane turned to correspondingalcohol and acid, acids were further changed to short-chain fatty acids, then the fatty acidsentered the TCA cycle.S6 could improve the degrading ability of the oil-degrading strains effectively when theymixed together. Infrared spectrum analysis revealed that S6 produced glucolipid in the process ofmetabolism. It was observed that S6 decreased the surface tension of water from 72 mN/m to33.9 mN/m with the critical micelle concentration (CMC) of 50mg/L. The measurement of oildisplacement and surface tension demonstrated that the fermented liquid had stable surfaceactivity at varying range of salinity, pH, amount of dissolved oxygen. The optimal culturecondition was obtained through orthogonal experiment: glucose 10g/L, urea 5g/L, KH₂PO₄ 1g/L,liquor of microelement 2mL, pH 8.0, water 1000mL; and the biosurfactant production underoptimal culture condition was 0.173g/L. The surface active matter maintaining the stability of surface activity locates mainly within the cell and on the surface of the cellular wall by atomaticforce microscopy. The stimulation from outside hydrocarbon speeded the release ofbiosurfactant.The characteristics experimental results of N7 showed that the addition of nutritious salt andmicroelement advanced degradation of naphthalene. Degradation efficiency approachedequilibrium when dissolved oxygen was over 4.3mg/L, while decreased as increasingnaphthalene mass concentration. Neutral and weak alkaline condition favored the biodegradation.N7 had a maximum degradation capability of 95.66% when treating 100mg/L naphthalenesolution after 72h. N7 could also degrade toluene, dimethylbenzene, phenol, 2,4-nitrophenols,benzyl acid, 1-naphthol and salicylic acid. The result of UV-Vis and GC-MS revealed that therewere two possible degradation pathways for naphthalene: one was phthalic acid pathway, and theother was that naphthalene first oxidized to 1,2-dihydroxynaphthalene, then the cleavage of ringscaused the formation of salicylic acid, catechol and 2-hydroxymuconic semial-dehyde. Finallythese metabolites entered the tricarboxylic acid cycle(TCA).